1. Field of the Invention
This invention relates to optic, and more particularly to lens assemblies.
2. Description of the Related Art
Exterior lighting systems typically employ in-ground or aboveground lighting fixtures to illuminate a walkway, building or other decorative features. In many applications, the exterior lens of such fixtures is in an area where its surface may come into contact with pedestrians, children and heat-sensitive objects. Whether such fixtures are in-ground or above ground, they must be designed with care to avoid injury or damage that may be caused by unacceptably high surface temperatures their exterior lens.
One typical solution to protect heat-sensitive objects from the light source is to include a protective lens assembly. The assembly typically establishes a predetermined distance between the light source and exterior lens to reduce thermal transfer between them. Thicker lenses and heat sinks may also be used to further reduce such thermal transfer. Or, additional lenses may be added between the light source and external lens. Unfortunately, as these partially enclosed assemblies cool after use, cool air is drawn into the assemblies resulting in corrosion-producing water vapor condensation.
A need still exists, however, to further reduce heat transfer between the light source and exterior lens without inadvertently creating internal vapor condensation.